1. Field of the Invention
This invention relates to a material handling vehicle such as an excavator and, more particularly, to a material handling vehicle having a lower truck chassis which includes a truck cab and an upper structure which includes an upper cab and a material handling implement, such vehicle having a single engine on the lower chassis which provides power for operation under the control of an operator in either cab.
2. Description of the Prior Art
Frequently, a heavy-duty material handling vehicle such as a crane or excavator includes a lower or truck chassis on which is horizontally pivotally mounted an upper structure that supports the desired material handling implement. The truck chassis is capable of being driven over the road or highway under the control of an operator in the main truck cab. An upper structure is mounted on the truck chassis by a swing bearing through which a center pin extends for relative movement with respect to the truck chassis. An upper structure operator's cab is provided on the upper structure to move with a material handling boom and implement. During operation at a construction site, an operator in the upper structure operator cab can control movement of the truck chassis and also the material handling mechanism.
Previously, in order to provide for remote operation from the upper structure cab of both the manipulations of the material handling mechanism as well as the movement of the entire vehicle, two separate engines were required. One engine was mounted on the truck chassis and controls the highway operation of the vehicle. A separate engine was mounted on the upper structure and provided motive power both to the material handling mechanism as well as powering, through a hydraulic pump and motor, the motion of the truck chassis. U.S. Pat. No. 3,599,814 teaches a remote drive mechanism for powering the drive wheels from an auxiliary engine mounted on the upper structure. U.S. Pat. No. 4,318,451 also teaches a material handling vehicle having a power supply on the upper structure which through a hydraulic motor drives the vehicle at the job site.
As is well known in the art, the previously unavoidable requirement of two separate engines, one on the truck chassis and one on the upper structure, was fraught with a host of disadvantages. For example, with the prior art construction requiring two separate engines the additional weight and cost of the auxiliary engine itself as well as duplicate fuel tanks, radiators, battery and charging systems, air compressors and dryers, power steering pumps, air cleaners and exhaust systems, controls, shroudings and mountings, noise barriers, engine gauges, etc. are incurred. In addition, duplicate maintenance functions are involved in a two-engine vehicle and operating costs are necessarily increased.
In an effort to overcome the problems associated with two engine excavators, the single engine excavator disclosed in U.S. Pat. No. 4,705,450 was developed. That patent discloses a drive train for an excavator having an engine mounted on a lower chassis which is coupled to an automatic powershift transmission. The disclosures of U.S. Pat. No. 4,705,450 are hereby incorporated herein by reference.
Despite the many advantages of the excavator disclosed in U.S. Pat. No. 4,705,405, there are features associated with the powershift transmission which could withstand improvement. For example, the powershift transmission and its required support system is relatively complicated and costly. As such, initial, maintenance, and repair/replacement costs for powershift transmissions are increased. Also, such transmissions consume energy which translates into lower excavator highway transport speeds and increased fuel usage.
The subject invention is directed toward an improved material handling apparatus which overcomes, among others, the above-discussed problems with material handling vehicles and which is effective to sufficiently power all customary remotely controlled functions of a material handling apparatus while requiring only one engine driving into a manual transmission.